While there could be various reasons as to why this error would be thrown during the upgrade of StoreFront to 3.7, one of the reasons that could cause this is if you have applied customizations to the UI of the legacy 2.6 StoreFront. The environment above environment had the following customization applied so that allow the applications were displayed and placed into appropriate folders:

The links to the ReceiverForWebFolderView.zip package in the above blog post no longer work so if you come across an environment with these customizations applied and not sure how it is configured, the following are the files bundled in the package:

The ReadMe.txt file contains the following instructions:

This folder contains customization files for Citrix Receiver for Web 2.5 to provide a folder view for a mandatory store:

custom.script.js

custom.style.css

custom.wrstrings.en.js

FolderClosed32.png

folderview.min.js

If you have not customized your Receiver for Web site, simply copy all the files to the contrib folder of your site.

If you have modified any of custom.script.js, custom.style.css and custom.wrstrings.en.js, you have to manually merge the files in the folder with your modified files and copy the remaining files.

In addition, if you need to support other languages, you have to translate the string "Main" and insert the translated string into custom.wrstrings.<lang-code>.js.

Disclaimer

==========

THESE FILES ARE PROVIDED "AS IS" WITHOUT WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED. CITRIX SYSTEMS, INC. ("CITRIX"), SHALL NOT BE LIABLE FOR TECHNICAL OR EDITORIAL ERRORS OR OMISSIONS CONTAINED HEREIN, NOR FOR DIRECT, INCIDENTAL, CONSEQUENTIAL OR ANY OTHER DAMAGES RESULTING FROM THE FURNISHING, PERFORMANCE, OR USE OF THESE FILES, EVEN IF CITRIX HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES IN ADVANCE.

The following files located in C:\inetpub\wwwroot\Citrix\<yourCitrixSite>Web\contrib are the ones that were replaced:

custom.script.js

custom.style.css

custom.wrstrings.en.js

FolderClosed32.png

folderview.min.js

The easiest way to get the original UI back is simply navigate to the \contrib folder of a Citrix StoreFront site that wasn’t customized and copy the files back over. If there are no additional StoreFront sites to use then create a new temporary one and copy the files over and ensure that are not additional files or folders left:

Once the files are over, restart the StoreFront server (an iisreset does not appear to be enough), rerun the upgrade and process should now complete: